Electrical system for compensating for line voltage variations



Nov. 24, 1959 A. KUSKO 2,914,722-

ELECTRICAL SYSTEM FOR COMPENSATING FOR LINE VOLTAGE VARIATIONS Filed May14, 1954 5 Sheets-Sheet 1.

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BY MMM 72:43:22; 7) m-roman INVENTOR Alexander fii'ako Nov. 24, 1959 A.KUSKO 2,914,722

ELECTRICAL SYSTEM FOR CONPENSATING 0R LINE VOLTAGE VARIATIQNS Filed May14. 1954 5 Sheets-Sheet s I Wan". I a'l'uo d y I I I I 0 I I I 4s 4INVENTOR Alexmcferfi'sko BY wma uffaza ATTORNEYS Nov. 24, 1959 A.KUSKO," 2,914,722

ELECTRICAL SYSTEM FOR COMPENSATING FOR LINE VOLTAGE VARIATIONS Filed May14, 1954 v 5 Sheets-Shoot 4 INVENTOR A/examrfiiw/za BY m M za fmATTORNEYS Nov. 24, 1959 A. KUSKO 2,914,722

ELECTRICAL SYSTEM FOR COMPENSATING FOR LINE VOLTAGE VARIATIONS Filed May14, 1954 5 Sheets-Sheet 5 I28 vwww \NVENTOR Alexander Xxx/ 0 BY BMW wATT RNEYS ,iOI161Of the objects of the invention is to provide a UnitedStates Patent Alexander Kusko, Newton Center, Mass. Application May 14,1954, Serial No. 429,731

, l0 8 Claims. (Cl. 323--66) This invention relates to systems forcompensating for variationsin line voltage and other factors in analternating;currentsupply system and particularly to an arrangement forcontrolling a resonantcircuit or static regulator in thesystem;

- It. is: desirable in certain load circuits, such as lighting circuits,to. provide arrangements to keep the current constant therein. Theregulation of lamp current within a relatively narrow range is importantin order to obtain reasonable lamp life and steady illumination. Inresonant constant. voltage to constant current transformation circuitmeans, such asthe arrangement known as a monocyclic: square, ifthe.potential supplied thereto is constant, the current will besubstantially constant, but if the potential, varies, there will'be avariation. inload current.

3O circuit. arrangement for a resonant circuit or static regulatorsystem in. which constant current will be supplied to thegloadregardless of variations, within limits, of line voltage and otherfactors- Another. object of the invention is to provide a circuitarrangement for a static type regulator of the resonantconstantvoltageto. constant current type, wherein changes inZtheloadcurrent are utilized to apply corrections to saturableelectro-magnetic devices in the system so as to maintain a constantapplied. current tothe load.

. .This application; isa continuation-in-part of application Serial-No.339,l-4.l,filed February 26, 1953.

In one aspect of the invention, a. source of alternating current isconnected to a. resonant constant voltage to constant currenttransformation circuit, the output of said 5 circuit being connected tothe load which, for example, may be a lighting load. The resonant,circuit may be a monocyclic square or. a. T circuit as will be describedhereafter. A current sensing. transformer or device is connected intheload'circuit for producing a signal proportional, to orfa function ofthe load current. This signal is'fedz to. a. means comparing andamplifying any: deviation therefrom to produce an indication signal. Themeans for producing the indication signal may be electro-mechanical,electronic,.a magnetic amplifier or other similar device. The signalfrom. thesensing and amplifying means is. applied: to the. directcurrent winding of a saturable electro-magneti'c means. As one example,the saturable el'ect'ro-magnet-ic means in the monocyclic square may; hein the form of saturable reactors. In another form, the outputtransformer between the resonant circuit and the load circuit may be asaturable transformer. The saturable electromagnetic devices concernedhave at least a control and a gate or load winding associated with acommonIcore.

These and other objects, features, and advantages of theinvention willbecome apparent from the following description and drawings, which aremerely exemplary.

In the drawings:

Fig. 1 diagrammatically shows one circuit arrangement of the invention.

Fig. 2 shows a set of curves illustrating the manner 2. in whichadjustment of the saturable reactor control current of Fig. 1 will causethe regulator to maintain sub.- stantially constant output currentirrespective of changes in the input voltage.

Fig. 3 is an alternative form of the signal producing device of Fig. 1.

Fig. 4 is a still further form of the signal arrangement suitable foruse in the circuit illustrated in Fig. 1.

Fig. 5 is a still further modification of a signal producingarrangement.

Fig. 6 illustrates another form of a resonant constant voltagetoconstant current transformation circuit, together with a saturabletransformer in place of control of saturable reactors in the monocyclicsquare of the previous figures.

Fig. 7 is a resonant constant voltage to constant current transformationcircuit similar to that of Fig. 6, except that the reactors therein havesaturable reactors in parallel thereto.

Fig. 8 is a still further circuit arrangement.

The arrangements involved are particularly concerned with supplying aconstant load current to a load by a resonant constant voltage toconstant current transformation circuit independent of load impedance.The resonant constant voltage to constant current transformation circuitmay be of the monocyclicsquare type wherein the input is connected totwo sides of a bridge arrangement having capacitors in opposite legs ofthe bridge and reactors in the other legs. It is also applicable to aresonant constant voltage to constant current transformation circuit ofthe T type, as will be explained hereafter. The T type has two reactorsin series with a capacitor corrector across the line and between saidreactors.

In these arrangements of resonant circuits, if the line voltage changes,theload current fromthe regulator will change proportionately, suchbeing very objectionable. Inasmuch as it is well known that line voltagewill not stay constant and may change asmuch as 10% either Way, therewill be a constant change in load current The supply frequency and thecapacitance and reactances of the resonant constant voltage to constantcurrent transformation device also may vary so that compensationtherefor must be provided for efiicient operation of the arrangement.

In one form of the invention, a monocyclic square is used whichv istuned by resonating the reactance of the inductors and capacitors thatare in the monocyclic square. Changing one, or the other sets ofelements alone from resonance, has been found to be an effective way tochange current level over a limited range, for example, :10% of thenormal current. Change of :30% in the reactance of the reactor from theresonance value is sufficient to compensate for a :10% change in linevoltage in order to maintain a constant load current.

In the form of the invention now being described, reactors in themonocyclic square can be of the saturable electro-magnetic type, thereactance thereof being varied by variation in a direct current controlwinding, such serving to regulate the load current. The direct currentcontrol can be operated by an arrangement which measures or senses theload current or produces a signal in proportion thereto, the signalbeing amplified and compared with a predetermined value to produce acorrective control current for the monocyclic square and saturablereactors. The latter will serve to restore the load current to itspredetermined constant valve. In this way, any change. in the loadcurrent caused by line voltage or other variation will be detected andcorrected.

In the example shown in Fig, 1, input transformer 1 may have a primarywinding 2, secondary winding 3, and control winding 4.. The monocyclicsquare A is connected to secondary winding 3 of input transformer 1. Themonocyclic square A may comprise four arms, two of which include reactorcircuits 6 and 7 and the other two of which include capacitors 8 and 9.Reactor circuits 6 and 7 each may comprise fixed reactors 11 and 14connected in parallel with saturable adjustable reactors and 15respectively. A fixed reactor is illustrated in parallel with asaturable reactor in the two arms of the square. It also is possible andpreferable that only saturable reactors be used in the reactor arms ofthe monocyclic square or T type circuit.

Saturable reactors 10 and 15 are controlled by direct current controlwindings 12 and 16. In the form illustrated, direct current is suppliedfrom control power winding 4 on input transformer 1 through adjustableresistor 18 and the rectifier 17. Adjustable resistor 18 is varied inaccordance with the position of contact arm 19 which in turn is actuatedby armature 20 and solenoid 21, the adjustable resistor arrangement thusbeing an electromechanical device. 7

The monocyclic square A has its output terminals connect to primarywinding 27 of output transformer 26. The secondary winding of outputtransformer 26 is connected to the power distribution or load circuit29.

The power distribution circuit 29 may include a control transformer 22,the primary thereof being in series with the secondary winding 28 ofoutput transformer 26. The secondary winding 31 of control transformer22 supplies power to solenoid 21 of the electro-mechanical devicethrough adjustable resistor 23. Solenoid 21 con trols position ofarmature 20 for positioning control 19 on resistor 18. The magneticcircuit of the solenoid 21 may be designed so that control arm 19 willcover its complete range on resistor 18 for a 2% or less change insolenoid current. It is important that the solenoid be extremelysensitive because otherwise too great a departure from de'sired'levelwould be required in load current and solenoid current in order toactuate the corrective action. Resistor 18 may be connected to a bridgetype rectifier 17, the rectifier receiving power from Winding 4 of theinput transformer 1.

Control transformer 22 preferably has an air-gap in its core so that theprimary current in winding 25 will be proportional to the secondaryvoltage across secondary winding 31. Resistor 23 is adjusted so that thedirect current in windings 12 and 16 on saturable reactor 10 and 15 willset the reactance of the saturable reactors to cause the monocyclicsquare to deliver the desired load current to load circuit 29. As theinput voltage, the frequency, or the capacitances or inductanceparameters in the monocyclic square change, the load current in loadcircuit 29 would tend to change and thus through control transformer 22move armature 20 to cause the direct current in saturable reactorwindings 12 and 16 to change so as to correct load current in loadcircuit 29. It can be seen that change in load current will result in achange in the rectified current received from rectifier 17 by thecontrol windings 12 and 16 of saturable reactors 10 and 15 so as tocontrol operation of the monocyclic square.

As an example of the manner of operation of the arrangement of Fig. 1,Fig. 2 shows characteristic curves and compensation of the system. Thesecurves show the manner in which adjustment of the saturable reactorcontrol current in windings 12 and 16 will cause the resonant constantvoltage to constant current transformation circuit to maintain constantoutput current regardless of changes in input line voltage. The curvesare plotted with input voltage as abscissas and control current ohms andamperes as ordinates. The curves have been plotted to show thecharacteristics of a 6.6 amp., 220 volt saturable reactor controlledsystem having the control current adjusted to maintain constant outputcurrent.

The set of curves shown at A illustrates the relationship between outputload current and input line current, it being noted that the output loadcurrent is constant.

The set of curves at B show the capacitor current in the monocyclicsquare as compared to the total reactor current in the fixed reactors 11and 14 and the saturable reactors 10 and 15.

The set of curves at D show the relationship of the saturable reactorcontrol current in windings 12 and 16 in their relation to the saturablereactor current of the circuit.

Fig. 3 illustrates another form of the invention wherein a signalproportional to the load circuit is used in conjunction with a magneticamplifier arrangement. Points B, B can be connected to B, B of Fig. 1,replacing the load circuit and control current determining arrangementthereof, points C, C being connected to the saturable electro-magneticdevice control winding. Output transformer 35 has its secondary 36connected to load circuit 37, said load circuit having a load 30therein. The current sensing transformer 38 has its primary 39 connectedin load circuit 37. The secondary 40 of the current sensing transformer38 is connected through an adjustable resistor 41 to bridge rectifier42. The rectifier output is connected to control winding 43 of themagnetic amplifier 44. The magnetic amplifier is shown conventionallywith two windings 45, 46 and control winding 43 and a second controlwinding 44' together with rectifier elements 45. Control winding 44 maybe connected to a source of direct current 46 for setting up a referencevoltage or bias on the magnetic amplifier 44. The magnetic amplifier 44is connected to the bridge rectifier 47, the output of the rectifier 47having leads indicated at C, C. The leads C, C, for example, may beconnected to points C, C of Fig. 1, which in turn are connected to thesaturable reactor control windings 12 and 16 of the resonant constantvoltage to constant current transformation circuit means thereof. Asource of alternating current 48 is connected to the magnetic amplifierand rectifier 47. Thus, a change in load current in the load circuit 37of Fig. 3 will provide a compared and amplified deviation of the signalfrom the current sensing transformer to produce an indication signalwhich will adjust the saturable reactors of the resonant constantvoltage to constant current transformation circuit means. The controlwindings of the magnetic amplifier are connected so that an increase inload current will reduce the saturating current delivered to thesaturable reactors in the regulator means. The current sensingtransformer also may have a tapped secondary in place of the variableresistor for setting load current.

Another form of control power supply in place of using power from theinput transformer is seen in Fig. 4 wherein terminals B, B leading tothe primary of output transformer 50 may be connected to B, B of Fig. 1to replace the load sensing portion. The secondary 51 of outputtransformer 50 is connected to load circuit 52 having load 53 therein.Current sensing transformer 54 has its primary 55 in the load circuit52, the secondary 56 being connected to solenoid 57. Solenoid 57controls the wiper or contactor 58 of the resistor 59, the contactorbeing connected with lead 60 similar to Fig. 1. Control powertransformer 61 has its primary 62 in the load circuit 52 and a secondary63 connected to rectifier 64 through the resistor 59. Thus, resistor 59and solenoid 57 are parts of the electro-mechanical regulatorarrangement. The output of the rectifier 64 can have terminals C, Cconnected to C, C of Fig. 1 so as to furnish control current to thecontrol windings 12 and 16 of the saturable reactors 10 and 15. In thisform, control power is taken from the regulated load circuit. If thecontrol power is relatively small compared to the load power, forexample, 1%, this form is very economical in operation.

Fig. 5 illustrates a further form of the invention in which anelectronic tube arrangement is employed to supply the control directcurrent to the control winding of the saturable reactor. Terminals B, Bthereof may beconnected to B, B or output of the monocyclic square ofFig. 1. Output transformer 64 has its secondary 66 connected to loadcircuit 67 having load 68 therein. The current sensing transformer 69has its primary 70 in load circuit 67, the secondary 71 being connectedto rectifier 72. The output of the rectifier has one side connected togrid 73 of the electronic tube 74. A variable resistor 75 is connectedacross the grid and the lead 76 from the other side of the rectifier tothe plate circuit D.C. supply 77. Cathode 78 of tube 74 is connected tolead 76 through a reference voltage source 79. Leads C, C may beconnected to points C, C of Fig. 1 to furnish the control DC. for thecontrol windings of the saturable reactor.

In addition to the monocyclic square arrangement described in Figure 1,a T type resonant constant voltage to constant current transformercircuit such as illustrated in Figure 6 can be used in place thereof.

In the embodiment shown in Figure 6, input power can be supplied toterminals by an input transformer such as 1 of Fig. 1 to the T typeresonant constant voltage to constant current transformation circuit D.This circuit comprises reactors 91 and 92 in series with primary 93 ofthe output transformer 94. A capacitor 95 is connected at one pointbetween reactors 91 and 92 and at its other side between primary 93 andterminal 90. In place of the usual output transformer as illustrated inFigure l, a saturable transformer 94 is illustrated having a DC. controlwinding 96. A saturable transformer arrangement is described in moredetail hereafter in conjunction with Fig. 8.

The secondary 97 of the output transformer 94 can be connected to theload circuit at points E, E of Figure 1. A current sen-sing transformerin the load circuit such as shown in Figure 1 then can be used to supplycontrol voltage at C, C of Figure l to the DC. control winding 96 at C',C of Figure 6.

Another form of resonant constant voltage to constant currenttransformer which can be used in place of the monocyclic square A inFigure 1, and the other forms, is seen in Figure 7. In this embodiment,input power supply is connected at leads 100 to the T type resonantconstant voltage to constant current transformer arrangement F havingfixed reactors 101 and 102 with saturable reactors 103 and 104 inparallel thereto. The saturable reactors have DC. control windings 105and 106. The load circuit or output transformers of the prior circuitsmay be connected at terminals 107. The current sensing transformerarrangement of the load circuit then may operate through its controlarrangements to produce, for example, control DC. at C, C of Figure 1which can be connected to each of the control windings 105 and 106 ofFigure 7.

The circuits of Figures 6 and 7 thus will produce a controlled loadcurrent from A.C. supply systems.

As another example of a complete circuit employing a saturabletransformer, reference may be made to Figure 8. The monocylic square Ghas reactors 108, 109 in two arms thereof and capacitors 110 and 111 inthe other arms thereof, said monocyclic square being supplied by asource of alternating current 112. The output of the monocyclic square Gis connected to saturable transformer 113, said saturable transformerhaving primary windings 114 and 115 connected to the opposite corners ofthe monocyclic square. secondaries 116 and 117 are connected in loadcircuit 118 having the load diagrammatically illustrated at 119. The DC.control winding 120 is inductively related to the windings of thesaturable transformer 113. Current sensing transformer 121 has itsprimary 122 in the load circuit, the secondary 123 being connected tosolenoid 124. Solenoid 124 may operate contact fingers 125 in devicessuch as the type shown as Regohm, having fingers which are connected tothe resistor 125 thereof.

Power for the control current may be supplied from the supply source 112through the control transformer 127. Bridge rectifier 128 suppliescontrol DC. to the control winding 120 in accordance with the currentflowing in the load circuit 118.

Merely by way of example, the saturable output transformer 113 can beone built on a 3 legged core with the control winding on the middle legand the alternating current winding on the outer two legs. One primaryand one secondaiy alternating current coil can be placed 011 each outerleg, the two primary coils being connected in series and the ,twosecondary coils connected in series in such a manner that there will beno induced line frequency voltage in the control windings.

It should be apparent that Variations may be made in the details ofconstruction and arrangement without departing from the spirit of theinvention except as defined in the appended claims.

I claim:

1. In a system for compensating for variations in an alternating currentsupply system with respect to a power distribution load circuit, thecombination including a resonant constant voltage to constant currenttransformation circuit means for feeding said load circuit, signal meansconnected to said load circuit producing a signal proportional to theload current in said load circuit, means comparing and amplifyingdeviation of said signal from a predetermined value to produce anindication signal, saturable reactor means in said resonant circuitmeans, and means connecting the control winding means of said saturablereactor with said means comparing and amplifying said signal.

2. In a system for compensating for variations in an alternating currentsupply system with respect to a power distribution load circuit, thecombination including a monocyclic square having four interconnectedarms with capacitors in two opposite arms and reactors in the other twoopposite arms, input supply means for said square, output load circuitconnections with said square, signal means connected to said loadcircuit producing a signal proportional to the load current in said loadcircuit, means comparing and amplifying deviation of said signal from apredetermined value to produce an indication signal, control windingsassociated with the arms having reactors in said square, and meanssupplying control current to said control windings in accordance withsaid indication signal for compensating through said monocyclic squarefor variations in said power supply system.

3. In a system for compensating for variations in a power supply systemwith respect to a power distribution circuit comprising an alternatingcurrent power supply system, a power transformer including a primarywinding and a pair of secondary windings, a monocyclic square includingfour interconnected arms in which two of said arms include reactorcircuits and the two opposite arms include capacitors, input terminalsfor said monocyclic square connected with one of said secondarywindings, output terminals for said monocyclic square connected to anoutput transformer, a power distribution circuit connected with saidlast-mentioned output transformer, a separate transformer included insaid power distribution circuit, a regulating circuit controlled by saidlastmentioned separate transformer, means for supplying energy to saidregulating circuit from one of the secondary windings on thefirst-mentioned transformer and control windings associated with thefirst-mentioned arms of said monocyclic square and electricallycontrolled from said regulating circuit for compensating through saidmonocyclic square for variations in said power supply system.

4. In a system for compensating for variations in a power supply systemwith respect to a power distribution circuit, as set forth in claim 3,in which the reactor circuits in the said first-mentioned arms of saidmonocyclic square include fixed reactors and saturable adjustablereactors, respectively, connected in parallel with said fixed reactorsand in which said control windings are inductively associated with saidsaturable adjustable reactors and receive control current from saidregulator circuit.

ings of said first-mentioned transformer, said regulating circuitincluding an adjustable resistor and a rectifier system therein andmeans controlled from the separate transformer in the power distributioncircuit for controlling the eifective value of said resistor and controlwindings coupled with the first-mentioned arms of said monocyclic squareand connected with the output of said rectifier for controlling theoperation of said monocyclic square in accordance with variationsincident upon said power distribution circuit and/or said power supplysystem.

6. In a system for compensating for variations in a power supply systemwith respect to a power distribution circuit, as set forth in claim 3,in which said regulating circuit includes a variable control elementconnected with said separate transformer, said means including aresistance and a rectifier, means controlled by said variable controlelement for controlling the eflective value of said resistance forcorrespondingly controlling the current impressed upon said rectifierand circuit connections from the output of said rectifier to saidcontrol windings in said monocyclic square for controlling the operationof said monocyclic square according to variations existent in said powerdistribution circuit.

7. In a system for compensating for variations in a power supply systemwith respect to a power distribution circuit, as set forth in claim 3,in which the regulating circuit includes a solenoid winding, an armaturecontrolled by said solenoid winding, a switch arm controlled by saidarmature, a resistance over which said switch arm operates, a rectifierhaving its input circuit included in series with said resistance andconnected with one of the secondary windings of said first-mentionedtransformer, and control windings inductively associated with thereactor circuits of the first-mentioned arms of said mono cyclic squareand electrically connected in series with the output of said rectifierwhereby the operation of said monocyclic square is compensatinglycontrolled through the operation of said regulating circuit.

8. The system set forth in claim 1 wherein the resonant constant voltageto constant current transformation circuit means comprises a pair ofsaturable reactors connected in series with the input and output of thetransformation circuit means and a capacitor is connected across saidinput between said reactors.

References Cited in the tile of this patent UNITED STATES PATENTS1,943,464 Ohlsen et al Jan. 16, 1934 2,312,416 Johnson Mar. 2, 19432,358,394 Haug Sept. 19, 1944 2,437,837 Saretzky Mar. 16, 1948 2,471,822Lang May 31, 1949 2,563,670 Albrand Aug. 7, 1951

